The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
In recent years, in order to provide service using a novel relay platform such as social networking service (SNS), one-person media, etc. in a high performance mobile device, there is a need for a greater bandwidth than conventional art.
For instance, Cisco Visual Networking Index 2018 has presumed that the number of network connection devices per person would increase more than 3.6 times according to the development of Internet of Things (IoT), 5G mobile communication network technology, etc. Further, internet data usage per month per person was presumed to reach 85 GB in 2022. It also expected that video contents occupying 70% of total data traffic in 2017 will increase to more than 80% in 2022.
When classified by destination, explosively increasing data traffic may go to the inside of data centers, between data centers, and between the data center and the user. 70% or more of the global data traffic is generated in the data center. Data generated worldwide are mostly based on activities such as production, processing, storage, authentication of data generated in the data center.
Optical interconnect solutions can tackle the current explosive increase in data traffic inside the data center. The optical interconnect solutions have already replaced copper based interconnect networks in long-haul and metropolitan communication networks. The optical interconnect solutions have gradually broadened their application with increase in bandwidth and the advancement of optical communication technology. Of such optical interconnect solutions, an optical transceiver is representative of long distance optical interconnect solutions.
From a viewpoint of the user, a typical optical transceiver has both electrical and optical interfaces. Interconnecting two physically separate points using the typical optical transceiver needs two optical transceivers and a patch cord for the generation of optical interconnect between these two optical transceivers. Both of the optical transceivers generally used in the art need to be designed and manufactured to meet with electro-optical characteristics of optical signals received and transmitted (‘transceived’) by the optical transceivers, respectively. In order to make sure the optical transceivers working properly, the user is supposed to carefully select a pair of optical transceivers. After installing one optical transceiver at one side, the user needs to select the other optical transceiver which suitably matches with the previously selected optical transceiver, and then, install the other optical transceiver at the other side.
Optical signals transmitted from one of the optical transceivers to the other need to be monitored in real time. Further, the strength of optical signals transmitted from a transmitter needs to be increased or decreased according to a condition of an optical link.
When adjusting the strength of optical signals according to the condition of the optical link, a monitoring photodetector (MPD) may be arranged near a light source of the transmitter and used. The MPD monitors the optical signals outputted from the light source in real time. Similar to a structure of the aforementioned optical transceiver, multi-level pulse amplitude modulation or PAM-N(N is a natural number of more than 2) technique-based optical transceivers still need to employ the MPD.
For instance, when employing a PAM-4 technique which utilizes the entire strength of signal by four levels, the strength of optical signals transmitted from a transmitter needs to be monitored and controlled in real time so as to assure a desired level of extinction ratio (ER) of the optical signals transmitted from the optical transceiver. Typically, this task is also governed by the use of MPD.
In order to perform real-time monitoring and control of the optical signals outputted from an optical transceiver, a typical optical transceiver needs an MPD at a position near an internal light source of the optical transceiver and further requires an optical system that allows to input a part of the optical signal emitted from the light source to the MPD.
Further, when the light source is a vertical emitting type laser rather than an edge-emitting type or in-plane type laser, it is even more difficult to implement optical coupling between the light source and the MPD. In other words, high volume production of optical transceivers based on vertical emitting type lasers are even harder, compared to optical transceivers based on edge-emitting type lasers.
A small form factor pluggable (SFP) type of AOC shown in FIG. 1 at (a), or a quad small form factor pluggable (QSFP) type of AOC shown in FIG. 1 at (b), each of which has a structure similar to the optical transceiver, includes an electrical interface only. Optical transceiver modules at both ends of the SPF AOC or the QSFP AOC need no constant monitoring of the optical output of the light source or other factors, because they go through complete testing and setup of optical components and electronic components during manufacturing. Therefore, an AOC having such a structure as described above can be easily installed and maintained while having substantially the same performance and functions as the optical transceiver.
Accordingly, there is a need for an optical module that takes advantages of the AOC described above and requires no MPD, and is capable of increasing light output-current linearity to thus improve optical coupling efficiency without any specific component involving a complicated structure and high cost.